Conventional components of wind turbines such as electrical machines, power converters, key boxes and etc. need to be cooled in order to dissipate the heat generated during operation. The cooling systems have to be designed to generate a cooling power that keeps the temperature of the wind turbine components to be cooled below a predefined maximum component temperature.
The present design praxis of cooling systems for wind turbines is based on a specifically defined maximum allowable ambient air temperature that may be e.g. 35° C. or 40° C. The cooling system is designed to keep the temperature of relevant components under a predefined maximum component temperature even at maximum power output where heat dissipation arising as a result of mechanical and electrical losses is at its maximum.
If the maximum allowable ambient air temperature is exceeded and the turbine is running at maximum power output where heat dissipation arising as a result of mechanical and electrical losses is at its maximum, the cooling system may not be able to keep the temperature of the component under a predefined maximum component temperature. In this situation a suitable response is required.
EP 1 918 581 A2 uses the above-described ambient air temperature as control input. If the ambient air temperature exceeds the defined maximum allowable ambient air temperature the wind turbine is shut off in order to cool down and to prevent overheating of the components. Further parameters, such as the temperature of the components itself or the capacity of the cooling system are not taken into consideration.
Besides the ambient air temperature, the temperature of the components may also be affected by the amount of generated output power of the component, the wind speed, the cooling capacity of the cooling system and a variety of other parameters, such as a blockage of coolers by dust or insects, etc. In conventional cooling systems these parameters were not drawn sufficiently into consideration in order to provide an appropriate cooling for components of the wind turbines.